apl

I have dummytxt←'abcdefghijk' texttoadd←'down' rfikv←20 30 50 and need following output defghijk20down defghijk30down defghijk50down I can do it with: scenv←(¯10↑¨(⊂dummytxt),¨⍕¨rfikv),¨⊂texttoadd but please help me to write without each operator but using rank ⍤ I use Dyalog APL, but please do not use trains. Thank you Expressions using Each , like f¨x , can be expressed in terms of Rank as {⊂f⊃⍵}⍤0⊢x (note that ⊢ is to separate the array right operand, 0 from the array right argument x ). In other words, on the scalars of the argument we: disclose the scalar: ⊃⍵ apply the function: f⊃⍵

I saw answer in this question How to use rank operator instead of each in APL how to build own Each operator using Rank ⍤ . Monadic Each f¨x can be represented as {⊂f⊃⍵}⍤0⊢x Dyadic Each x f¨y can be represented as x{⊂(⊃⍺)f(⊃⍵)}⍤0⊢y In terms of this please answer following questions: Why Each ¨ operator can be represented as Each←{⍺←⊢ ⋄ ⍺ ⍺⍺{×⎕NC'⍺':⊂(⊃⍺)⍺⍺(⊃⍵) ⋄ ⊂⍺⍺⊃⍵}⍤0⊢⍵} What means ⍺⍺ in the expression above Thank you in advance for your answers. This definition basically combines the monadic and dyadic cases which you listed above. ×⎕NC'⍺' will return 1 if ⍺ exists and 0 otherwise, so it

Is there a symbol or well-known idiom for the conditional function, in any of the APL dialects? I'm sure I'm missing something, because it's such a basic language element. In other languages it's called conditional operator , but I will avoid that term here, because an APL operator is something else entirely. For example C and friends have x ? T : F LISPs have (if x T F) Python has T if x else F and so on. I know modern APLs have :If and friends, but they are imperative statements to control program flow: they don't return a value, cannot be used inside an expression and certainly cannot be