Rust Iterator Cheat Sheet

IT $\text{batching}$ $\{\underbrace{a_0,\dots },\underbrace{a_i,\dots },\dots \}:\{T\}$, $batch:\text{\&mut }\{T\}\to U$ $\{\underset{batch(\{a_0,\dots \})}{\underbrace{c_0}},\underset{batch(\{a_i,\dots \})}{\underbrace{c_1}},\dots \}:\{U\}$ IT $\text{cartesian\_product}$ $\{a_0,a_1,\dots ,a_{n-1}\}$, $\{b_0,b_1,\dots ,b_{m-1}\}$ $$\begin{gathered} \{(a_0,b_0),(a_0,b_1),\dots ,(a_0,b_{m-1}), \\ (a_1,b_0),(a_1,b_1),\dots ,(a_1,b_{m-1}) \\ \dots , \\ (a_{n-1},b_0),(a_{n-1},b_1),\dots ,(a_{n-1},b_{m-1})\} \end{gathered}$$ Std $\text{chain}$ $\{a_0,\dots ,a_{n-1}\}$, $\{b_0,\dots ,b_{m-1}\}$ $\{a_0,\dots ,a_{n-1},b_0,\dots ,b_{m-1}\}$ IT $\text{chunks}$ $\{a_0,\dots \}$, $m$ $\{\{a_0,\dots ,a_{m-1}\},\{a_m,\dots ,a_{2m-1}\},\dots \}$ Std $\text{cmp}$ $\{a_0,\dots ,a_i\}$, $\{b_0,\dots ,b_i,b_{i+1},\underset{\_}{\dots }\}$ $\text{cmp}(a_0,b_0)\text{ then }\dots \text{ then }\text{cmp}(a_i,b_i)\text{ then }\text{Less}$ $\{a_0,\dots ,a_i\}$, $\{b_0,\dots ,b_i\}$ $\text{cmp}(a_0,b_0)\text{ then }\dots \text{ then }\text{cmp}(a_i,b_i)\text{ then }\text{Equal}$ $\{a_0,\dots ,a_i,a_{i+1},\underset{\_}{\dots }\}$, $\{b_0,\dots ,b_i\}$ $\text{cmp}(a_0,b_0)\text{ then }\dots \text{ then }\text{cmp}(a_i,b_i)\text{ then }\text{Greater}$ IT $\text{coalesce}$ $\{a_0,a_1,a_2,\dots \}$ $f:(T,T)\to \text{Ok}(T)|\text{Err}((T,T))$ $\begin{array}{llcl}& \{x_0,\dots \}& \text{wh.}& \{\begin{array}{l}f(a_0,a_1)=\text{Ok}(x_0),\\ \dots \end{array}\\ \text{or}& \{a_0^{\prime },x_1,\dots \}& \text{wh.}& \{\begin{array}{l}f(a_0,a_1)=\text{Err}((a_0^{\prime },a_1^{\prime })),\\ f(a_1^{\prime },a_2)=\text{Ok}(x_1),\\ \dots \end{array}\\ \text{or}& \{a_0^{\prime },a_1^{″},\dots \}& \text{wh.}& \{\begin{array}{l}f(a_0,a_1)=\text{Err}((a_0^{\prime },a_1^{\prime })),\\ f(a_1^{\prime },a_2)=\text{Err}(a_1^{″},a_2^{\prime }),\\ \dots \end{array}\end{array}$ Std $\text{collect}$ $\{a_0,\dots \}$ $[a_0,\dots ]$ IT $\text{collect\_vec}$ $\{a_0,\dots \}$ $[a_0,\dots ]:\text{Vec}⟨T⟩$ Std $\text{cycle}$ $\{a_0,\dots ,a_{n-1}\}$ $\{a_0,\dots ,a_{n-1},a_0,\dots ,a_{n-1},\dots \}$ IT $\text{dedup}$ $\{\underbrace{a_0,a_0,\dots },\underbrace{a_1,a_1,\dots },\dots \}$ $\{a_0,a_1,\dots \}$ IT $\text{dropping}$ $\{\underset{\text{consumed}}{\underbrace{a_0,\dots ,a_{i-1}}},a_i,\dots \}$ $i\text{ wh. }i<n$ $\{a_i,\dots \}$ (consumes $a_0\dots a_{i-1}$ immediately) $\{\underset{\text{consumed}}{\underbrace{a_0,\dots ,a_{n-1}}}\}$ $i\text{ wh. }i\ge n$ $\{\}$ (consumes $a_0\dots a_{n-1}$ immediately) IT $\text{dropping\_back}$ $\{a_0,\dots ,a_{n-i-1},\underset{\text{consumed}}{\underbrace{a_{n-i},\dots ,a_{n-1}}}\}$ $i\text{ wh. }i<n$ $\{a_0,\dots ,a_{n-i-1}\}$ (consumes $a_{n-i}\dots a_n$ immediately) $\{\underset{\text{consumed}}{\underbrace{a_0,\dots ,a_{n-1}}}\}$ $i\text{ wh. }i\ge n$ $\{\}$ (consumes $a_0\dots a_n$ immediately) Std $\text{enumerate}$ $\{a_0,a_1,\dots \}$ $\{(0,a_0),(1,a_1),\dots \}$ Std $\text{eq}$ $\{a_0,\dots ,a_{n-1}\}$, $\{b_0,\dots ,b_{m-1}\}$ $\text{false}\text{ wh. }n\ne m$ $(a_0=b_0)\wedge \dots \wedge (a_{n-1}=b_{n-1})$ Std $\text{filter}$ $\{a_0,a_1,\dots \}$, $p:\text{\&}T\to \text{bool}$ $\{a_i\text{ for all }i\text{ wh. }p(\text{\&}{a}_i)\}$ Std $\text{filter\_map}$ $\{a_0,a_1,\dots \}$, $f:T\to \text{Some}(U)|\text{None}$ $\{x_i\text{ for all }i\text{ where }f(a_i)=\text{Some}(x_i)\}$ Std $\text{flat\_map}$ $\{a_0,a_1,\dots \}$, $f:T\to \{U\}$ $\{\underset{x=f(a_0)}{\underbrace{x_0,x_1,\dots }},\underset{y=f(a_1)}{\underbrace{y_0,y_1,\dots }},\dots \}$ IT $\text{flatten}$ $\{\{a_0,\dots \},\{b_0,\dots \},\dots \}$, $\{a_0,\dots ,b_0,\dots \}$ Std $\text{ge}$ $\{a_0,\dots ,a_{n-1}\}$, $\{b_0,\dots ,b_{m-1}\}$ $\text{false}\text{ wh. }n<m$ $(a_0\ge b_0)\wedge \dots \wedge (a_{n-1}\ge b_{n-1})$ IT $\text{group\_by}$ $\{\underset{g(a_x)=g_0}{\underbrace{a_0,\dots ,a_{i-1}}},\underset{g(a_y)=g_1\ne g_0}{\underbrace{a_i,\dots ,a_{j-1}}},\underset{g(a_z)=g_2\ne g_1}{\underbrace{a_j,\dots ,a_{k-1}}},\dots \}$, $g:\text{\&}T\to G$ $$\begin{gathered} \{(g_0,\{a_0,\dots ,a_{i-1}\}), \\ (g_1,\{a_i,\dots ,a_{j-1}\}), \\ (g_2,\{a_j,\dots ,a_{k-1}\}),\dots \} \end{gathered}$$ Std $\text{gt}$ $\{a_0,\dots ,a_{n-1}\}$, $\{b_0,\dots ,b_{m-1}\}$ $\text{false}\text{ wh. }n<m$ $(a_0>b_0)\wedge \dots \wedge (a_{n-1}>b_{n-1})$ IT $\text{interleave}$ $\{a_0,a_1,\dots ,a_{i-1},a_i,\dots \}$, $\{b_0,b_1,\dots ,b_{i-1}\}$ $\{a_0,b_0,a_1,b_1,\dots ,a_{i-1},b_{i-1},a_i,\dots \}$ $\{a_0,a_1,\dots ,a_{i-1}\}$, $\{b_0,b_1,\dots ,b_{i-1}\}$ $\{a_0,b_0,a_1,b_1,\dots ,a_{i-1},b_{i-1}\}$ $\{a_0,a_1,\dots ,a_{i-1}\}$, $\{b_0,b_1,\dots ,b_{i-1},b_i,\dots \}$ $\{a_0,b_0,a_1,b_1,\dots ,a_{i-1},b_{i-1},b_i,\dots \}$ IT $\text{interleave\_shortest}$ $\{a_0,a_1,\dots ,a_{i-1},a_i,\underset{\_}{\dots }\}$, $\{b_0,b_1,\dots ,b_{i-1}\}$ $\{a_0,b_0,a_1,b_1,\dots ,a_{i-1},b_{i-1},a_i\}$ $\{a_0,a_1,\dots ,a_{i-1}\}$ $\{b_0,b_1,\dots ,b_{i-1},\underset{\_}{b_i,\dots }\}$ $\{a_0,b_0,a_1,b_1,\dots ,a_{i-1},b_{i-1}\}$ IT $\text{intersperse}$ $\{a_0,a_1,\dots ,a_{n-1}\}$ $b$ $\{a_0,b,a_1,b,\dots ,b,a_{n-1}\}$ IT $\text{kmerge}$ $$\begin{gathered} \{\{a_0,\dots \},\{b_0,\dots \},\dots \}\text{ wh.} \\ \text{sorted}(a),\text{ sorted}(b),\dots \end{gathered}$$ $$\begin{gathered} \{c_0,c_1,\dots \}\text{ wh. }{c}_0\le c_1\le \dots , \\ a\subseteq c,b\subseteq c,\dots \end{gathered}$$ IT $\text{kmerge\_by}$ $$\begin{gathered} \{\{a_0,\dots \},\{b_0,\dots \},\dots \}\text{ wh.} \\ \text{sorted\_by}(a,\circ ),\text{ sorted\_by}(b,\circ ),\dots \end{gathered}$$, $\circ :(\text{\&}T,\text{\&}T)\to \text{bool}$ $$\begin{gathered} \{c_0,c_1,\dots \}\text{ wh. }{c}_0\circ c_1\circ \dots , \\ a\subseteq c,b\subseteq c,\dots \end{gathered}$$ Std $\text{map}$ $\{a_0,a_1,\dots \}$, $f:T\to U$ $\{f(a_0),f(a_1),\dots \}$ IT $\text{map\_fn}$ $\{a_0,a_1,\dots \}$, $f:\text{fn}(T)\to U$ $\{f(a_0),f(a_1),\dots \}$ IT $\text{map\_results}$ $\{a_0,\dots \}:\{\text{Ok}(T)|\text{Err}(E)\}$, $f:(T)\to U$ $\{a_0.\text{map}(f),\dots \}:\{\text{Ok}(U)|\text{Err}(E)\}$ IT $\text{merge}$ $\{a_0,a_1,\dots \}\text{ wh. }{a}_0\le a_1\le \dots$, $\{b_0,b_1,\dots \}\text{ wh. }{b}_0\le b_1\le \dots$ $\{c_0,c_1,\dots \}\text{ wh. }{c}_0\le c_1\le \dots ,a\subseteq c,b\subseteq c$ IT $\text{merge\_by}$ $\{a_0,a_1,\dots \}\text{ wh. }{a}_0\circ a_1\circ \dots$, $\{b_0,b_1,\dots \}\text{ wh. }{b}_0\circ b_1\circ \dots$, $\circ :(\text{\&}T,\text{\&}T)\to \text{Ordering}$ $\{c_0,c_1,\dots \}\text{ wh. }{c}_0\circ c_1\circ \dots ,a\subseteq c,b\subseteq c$ IT $\text{pad\_using}$ $\{a_0,\dots ,a_{n-1}\}$, $m$, $$ $f:i\to T$ $$\begin{gathered} \{a_0,\dots ,a_{n-1}\}\text{ wh. }n>=m \\ \{a_0,\dots ,a_{n-1},f(n),\dots ,f(m-1)\}\text{ otherwise} \end{gathered}$$ Std $\text{partial\_cmp}$ $\{a_0,\dots ,a_i\}$, $\{b_0,\dots ,b_i,b_{i+1},\underset{\_}{\dots }\}$ $\text{pcmp}(a_0,b_0)\text{ then }\dots \text{ then }\text{pcmp}(a_i,b_i)\text{ then }\text{Less}$ $\{a_0,\dots ,a_i\}$, $\{b_0,\dots ,b_i\}$ $\text{pcmp}(a_0,b_0)\text{ then }\dots \text{ then }\text{pcmp}(a_i,b_i)\text{ then }\text{Equal}$ $\{a_0,\dots ,a_i,a_{i+1},\underset{\_}{\dots }\}$, $\{b_0,\dots ,b_i\}$ $\text{pcmp}(a_0,b_0)\text{ then }\dots \text{ then }\text{pcmp}(a_i,b_i)\text{ then }\text{Greater}$ Std $\text{partition}$ $\{a_0,a_1,\dots \}$, $f:\text{\&}T\to \text{bool}$ $$\begin{gathered} ([a_i\text{ for all }i\text{ wh. }f(\text{\&}{a}_i)=\text{true}], \\ [a_i\text{ for all }i\text{ wh. }f(\text{\&}{a}_i)=\text{false}]) \end{gathered}$$ IT $\text{partition\_map}$ $\{a_0,a_1,\dots \}$, $f:T\to \text{Left}(L)|\text{Right}(R)$ $$\begin{gathered} ([x_i\text{ for all }i\text{ wh. }f(a_i)=\text{Left}(x_i)], \\ [x_i\text{ for all }i\text{ wh. }f(a_i)=\text{Right}(x_i)]) \end{gathered}$$ Std $\text{rev}$ $\{a_0,a_1,\dots ,a_{n-2},a_{n-1}\}$ $\{a_{n-1},a_{n-2},\dots ,a_1,a_0\}$ Std $\text{scan}$ $\{a_0,a_1,\dots \}$, $s:\text{\&mut }S$, $f:(\text{\&mut }S,T)\to \text{Some}(U)|\text{None}$ $\{x_i\text{ for all }i\text{ wh. }f(s,a_i)=Some(x_i)\}$ Std $\text{skip}$ $\{a_0,\dots ,a_{i-1},a_i,\dots \}$, $i$ $\{a_i,\dots \}$ $\{a_0,\dots ,a_{n-1}\}$, $i\text{ wh. }i\ge n$ $\{\}$ Std $\text{skip\_while}$ $\{a_0,\dots ,a_i,\dots \}$, $p:\text{\&}T\to \text{bool}$ $\{a_i,\dots \}\text{ wh. }i\text{ is first wh. }p(\text{\&}{a}_i)$ IT $\text{sorted}$ $\{a_0,\dots \}$ $[c_0,\dots ]:\text{Vec}⟨T⟩\text{ wh. }{c}_0\le c_1\le \dots$ IT $\text{sorted\_by}$ $\{a_0,\dots \}$ $\circ :(\text{\&}T,\text{\&}T)\to \text{Ordering}$ $[c_0,\dots ]:\text{Vec}⟨T⟩\text{ wh. }{c}_0\circ c_1\circ \dots$ IT $\text{step}$ $\{a_0,\dots ,a_m,\dots ,a_{2m},\dots \}$, m $\{a_0,a_m,a_{2m},\dots \}$ Std $\text{take}$ $\{a_0,\dots ,a_{i-1},\underset{\_}{a_i,\dots }\}$, $i$ $\{a_0,\dots ,a_{i-1}\}$ $\{a_0,\dots ,a_{n-1}\}$, $i\text{ wh. }i\ge n$ $\{a_0,\dots ,a_{n-1}\}$ Std $\text{take\_while}$ $\{a_0,\dots ,a_{i-1},a_i,\underset{\_}{\dots }\}$, $p:\text{\&}T\to \text{bool}$ $\{a_0,\dots ,a_{i-1}\}\text{ wh. }i\text{ is first wh. }p(\text{\&}{a}_i)=\text{false}$ IT $\text{take\_while\_ref}$ $\text{\&mut }\{a_0,\dots ,a_{i-1},\underset{\_}{a_i,\dots }\}$, $p:\text{\&}T\to \text{bool}$ $\{a_0,\dots ,a_{i-1}\}\text{ wh. }i\text{ is first wh. }p(\text{\&}{a}_i)=\text{false}$ IT $\text{tee}$ $\{a_0,a_1,\dots \}$ $(\{a_0,a_1,\dots \},\{a_0,a_1,\dots \})$ IT $\text{tuple\_windows}$ $\{a_0,\dots \}$ $⟨(\underset{n}{\underbrace{\mathrm{\_},\mathrm{\_},\dots }})⟩$ $\{(a_0,\dots ,a_{n-1}),(a_1,\dots ,a_n),\dots \}$ IT $\text{tuples}$ $\{a_0,\dots \}$ $⟨(\underset{n}{\underbrace{\mathrm{\_},\mathrm{\_},\dots }})⟩$ $\{(a_0,\dots ,a_{n-1}),(a_n,\dots ,a_{2n-1}),\dots \}$ IT $\text{unique}$ $\{a_0,\dots \}$ $\{a_i\text{ for all }i\text{ wh. }{a}_i\notin \{a_0,\dots ,a_{i-1}\}\}$ IT $\text{unique\_by}$ $\{a_0,\dots \}$, $f:\text{\&}T\to U$ $\{a_i\text{ for all }i\text{ wh. }f(a_i)\notin \{f(a_0),\dots ,f(a_{i-1})\}\}$ Std $\text{unzip}$ $\{(a_0,b_0),(a_1,b_1),\dots \}$ $([a_0,a_1,\dots ],[b_0,b_1,\dots ])$ IT $\text{while\_some}$ $\{a_0,\dots ,a_{i-1},a_i,\underset{\_}{\dots }\}$, $\begin{array}{l}\{x_j\text{ for all }j<i\text{ wh. }{a}_j=Some(x_j)\}\\ \text{ wh. }i\text{ is the first wh. }{a}_i=\text{None}\end{array}$ IT $\text{with\_position}$ $\{a_0\}$ $\{\text{Only}(a_0)\}$ $\{a_0,a_1,\dots ,a_{n-2},a_{n-1}\}$ $$\begin{gathered} \{\text{First}(a_0),\text{Middle}(a_1),\dots , \\ \text{Middle}(a_{n-2}),\text{Last}(a_{n-1})\} \end{gathered}$$ Std $\text{zip}$ $\{a_0,\dots ,a_i\}$, $\{b_0,\dots ,b_i,\underset{\_}{b_{i+1},\dots }\}$ $\{(a_0,b_0),\dots ,(a_i,b_i)\}$ $\{a_0,\dots ,a_i,a_{i+1},\underset{\_}{\dots }\}$, $\{b_0,\dots ,b_i\}$ IT $\text{zip\_eq}$ $\{a_0,\dots ,a_{n-1}\}$, $\{b_0,\dots ,b_{m-1}\}$ $$\begin{gathered} \{(a_0,b_0),\dots ,(a_{n-1},b_{n-1})\}, \\ \text{panic wh. }n\ne m \end{gathered}$$ IT $\text{zip\_longest}$ $\{a_0,\dots ,a_{i-1},a_i,\dots \}$, $\{b_0,\dots ,b_{i-1}\}$ $\{\text{Both}(a_0,b_0),\dots ,\text{Both}(a_{i-1},b_{i-1}),\text{Left}(a_i),\dots \}$ $\{a_0,\dots ,a_{i-1}\}$, $\{b_0,\dots ,b_{i-1}\}$ $\{\text{Both}(a_0,b_0),\dots ,\text{Both}(a_{i-1},b_{i-1})\}$ $\{a_0,\dots ,a_{i-1}\}$, $\{b_0,\dots ,b_{i-1},b_i,\dots \}$ $\{\text{Both}(a_0,b_0),\dots ,\text{Both}(a_{i-1},b_{i-1}),\text{Right}(b_i),\dots \}$