[int_19h]

Curiously, higher-order functions, and the concept of something like a closure, dates back to the earliest days of PL design - and I'm not even talking about Lisp! Algol-60, the granddaddy of pretty much every modern mainstream programming language, already had the notion of nested functions (which closed over variables from the surrounding scopes) and the ability to pass those functions to other functions.

They weren't fully first-class because there were no function-typed variables, nor could you return a function. Even so, this already lets you do stuff like map and filter. And Algol-60 programs from that era did use those capabilities, e.g.:

  PROCEDURE EULER (FCT, SUM, EPS, TIM)
   VALUE EPS, TIM;
   INTEGER TIM;
   REAL PROCEDURE FCT;
   REAL SUM, EPS;
  BEGIN
   INTEGER I, K, N, T;
   ARRAY M [0 .. 15];
   REAL MN, MP, DS;
   I := N := T := 0;
   M[0] := FCT(0);
   SUM := M[0] / 2;
  NEXTTERM:
   I := I+1; 
   MN := FCT(1);
   FOR K := 0 STEP 1 UNTIL N DO
   BEGIN
    MP := (MN + M[K]) / 2;
    M[K] := MN;
    MN := MP
   END;
   IF (ABS(MN) < ABS(M[N]) AND N < 15) THEN
   BEGIN
    DS := MN/2;
    N := N+1;
    M[N] := MN
   END
   ELSE
    DS := MN;
   SUM := SUM + DS;
   IF ABS(DS) < EPS THEN
    T := T + 1
   ELSE
    T := 0;
   IF T < TIM THEN
    GOTO NEXTTERM
  END;