Re: Command Languages Versus Programming Languages

ram@zedat.fu-berlin.de (Stefan Ram) wrote or quoted:

( SETQ DIFF
 ( LAMBDA( X )
   ( COND
     ( ( ATOMP X )
       ( COND
         ( ( = X 'X )
           1 )
         ( T
           0 )))
     ( T
       ( COND
         ( ( =( CAR X )'SUM )
           ( LIST 'SUM( DIFF( CADR X ))( DIFF( CADDR X )))))))))

  In Python:

def diff( x ):
    return 1 if x == 'x' else 0 if type( x )is str
    else[ 'sum', diff( x[ 1 ]), diff( x[ 2 ])]
    if x[ 0 ]== 'sum' else None

  . An attempt at indentation:

def diff( x ):
    return \
            1 if x == 'x' else 0 \
        if type( x )is str else \
           [ 'sum', diff( x[ 1 ]), diff( x[ 2 ])] \
           if x[ 0 ]== 'sum' else None

  . In a multiple-returns style:

def diff( x ):
    if type( x )is str:
        if x == 'x':
            return 1
        else:
            return 0
    else:
        if x[ 0 ]== 'sum':
            return [ 'sum', diff( x[ 1 ]), diff( x[ 2 ])]

  .