The Python language has a neat feature: An expression like
x < y <= z is interpreted, according to mathematical convention, as equivalent to
x < y and y <= z. Operands are evaluated only as many times as they appear, and the short-circuiting nature of the equivalent operation is maintained. For example,
if f() <= g() < h() <= i(): whatever
behaves as if the code were
x1 = f() x2 = g() if x1 <= x2: x3 = h() if x2 < x3: x4 = i() if x3 <= x4: whatever
i() aren't evaluated unless necessary.)
As far as I am aware, the first language to support this was CPL, as demonstrated on page 6.1.3 of the CPL working papers. However, CPL was never implemented fully, so it could be argued that the feature was never supported, per se. Were there earlier examples?