As is described on another page, Mathyma provides the ability to print a large number of , such as order symbols: " " by typing their symbol indicators: " >. , &ge. , &le. , <. ".
One problem with this is that, apart from being a lot to type, in an expression of the form:
~x &ge.  . ~y &imply.  . ~x &ge. ~y or ~x &eq. ~y
the meaning doesn't exactly jump out at you. To improve matters a bit, Mathyma substitutes a number of short-ish text strings with more complicated ones, so the above example could be written:
~x >= ~y _ => _ ~x > ~y or ~x = ~y
which will appear as
| ~x >= ~y _ => _ ~x > ~y or ~x = ~y |
I don't know about you, but, to me, the second option looks a lot closer to the final result than the first one does.
String substitution is the first operation Mathyma carries out on the source text. The main advantage is the one outlined above, but it is also a way of getting around certain , of which more later. But first here is a list of the substitutions Mathyma makes.