* [`@custom xxx("...",<{...}>,...)`](https://github.com/user19870/cppsp/blob/First/example/custom...) : @custom can let users write own syntaxs. *"..." can generate code, <{...}> is similar to it but will become a placeholder and replaced by parameter when the custom syntax is called.Code will generate in global and the inner of some cppsp keywords. namespace only accept one level like: ` namespace n{ @custom.... }` ``` @custom subs(<{T}>," sub(",<{T a}>,",",<{T b}>,")"," {return a-b;}") subs(int ,int a,int b) ```