# Implementing vector-for-each in PLT

François asked how one might implement vector-for-each. Here are two solutions that were provided:
Matthias

```#lang scheme
(define-syntax for-each-vector
(syntax-rules ()
((for-each-vector proc vec ...)
(let ((len (min (vector-length vec) ...)))
(do ((index 0 (+ index 1)))
((= index len))
(proc (vector-ref vec index) ...))))))
(for-each-vector
(lambda (a b) (display (+ a b)))
#( 1 2 3)  #( 1 2 3))
(newline)
;; functional, preferred
;; for-each-vector2
;; (All (A C ...) ((C ... -> A) (Vectorof C) ... -> A))
(define (for-each-vector2 p . vec)
(for ((i (in-range (apply min (map vector-length vec)))))
(apply p (map (lambda (v) (vector-ref v i)) vec))))
(for-each-vector2
(lambda (a b) (display (+ a b)))
#( 1 2 3)  #( 1 2 3))
(newline)
```

Sam TH

```#lang scheme
(require srfi/43)
(for ([a #(1 2 3)] [b #(1 2 3)])
(display (+ a b)))
(newline)
(vector-for-each
(lambda (i a b) (display (+ a b)))
#(1 2 3) #(1 2 3))
```

## 2 thoughts on “Implementing vector-for-each in PLT”

1. And a stock standard R6RS one:
(define (vector-for-each p vec1 . vecs)
(let ((len (vector-length vec1)))
(do ((i 0 (fx+ i 1)))
((fx=? i len))
(if (null? vecs)
(p (vector-ref vec1 i))
(apply p (map (lambda (x) (vector-ref x i))
(cons vec1 vecs)))))))

2. Grant says:

Thanks Leppie.