Pegtop math components includes TpegtopFormula, the fastest1 expression evaluator available for Delphi
(there is a comparison of popular parsers at cc.borland.com written by Alexei Cioina).
This is done by compiling the expression (given as a string) to machine code at runtime - TpegtopFormula includes a real mini compiler.
To evaluate expresions TPegtopFormula makes use of the 80x87 FPU, the math coprocessor which is part of the CPU (since Intel included it to the 80386 CPU).
TPegtopFormula offers a property to get the machine code created, so you can see the asm instructions your expression was compiled to.
Different parsers evaluate different expressions with different speed. TPegtopFormula belongs to the fastest ones and for a great number of expressions there is no faster one according to the test application mentioned above.