Squaring the circle the circular arc b around O with radius , it results S'. Bisect the line segment in D and draw the semicircle b over D. Draw a straight line from O through C up to the semicircle b, it cuts b in E. The line segment is the mean proportional between and , also called geometric mean. Extend the line segment beyond O and transfer twice more, it results F and A, and thus the length of the line segment with the above described approximation value of formula_3, the half circumference of the circle. Bisect the line segment in G
Straight-line grammar definition of the more general formalism of straight-line context-free tree grammars can be found in Lohrey et al. An SLG in Chomsky normal form is equivalent to a straight-line program. Straight-line grammar A straight-line grammar (sometimes abbreviated as SLG) is a formal grammar that generates exactly one string. Consequently, it does not branch (every non-terminal has only one associated production rule) nor loop (if non-terminal "A" appears in a derivation of "B", then "B" does not appear in a derivation of "A"). Straight-line grammars are widely used in the development of algorithms that execute directly on compressed structures (without prior