Strings vs expressions

rice peter.rice at
Mon Feb 19 15:54:15 UTC 2001

James Bonfield wrote:
> When is a expression within a string a real expression, and when is it just
> part of the string?
> Mostly complex expressions are wrapped in @(), but not always. Eg see
> transeq.acd:
>         def: $(sequence.begin)-$(sequence.end)

This is a silly one - it only looks like an expression.

$(name) is replaced by the variable value

@(expression) is replaced by the expression result

The example you give ends up as something like "1-1000" in a string. It is
not an expression. Maybe we should call it a grimace :-)

When () are nested, the inner ones are always evaluated first.

$ or @ on their own, with no (), are unchanged.

Peter Rice, LION Bioscience Ltd, Cambridge, UK
peter.rice at +44 1223 224723

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